1. Field of the Invention
The present invention relates generally to patient monitoring and, more particularly, to systems, methods and apparatus for improved patient monitoring utilizing sensor-based adaptive wearable devices.
2. Description of the Related Art
During a mass emergency, many injured people must be helped in a quick and efficient manner. A clever triage system proficiently chooses the order in which individuals are sent to the hospital. A valuable triage also defines an effective system that distributes limited medical resources in a manner that helps as many people as possible. At a disaster scene, it is critical that patients are correctly diagnosed, monitored, and located to ensure the preservation of the maximum number of lives. Unfortunately, the current systems use paper triage tags that inefficiently monitor and locate patients during mass casualty situations.
In a mass casualty situation, the rapid and accurate triage (counting and sorting) of patients is the critical early step in the emergency response process. As noted above, the paper triage tags currently in use by EMS groups, however, are far from efficient. In the paper triage tag system, a first responder attaches a paper tag or colored ribbon to each patient. The first responder then calls the triage officer and reports the patient count. The commander tallies the patient numbers and calls for the necessary number of ambulances. Paper tags employ color codes to determine the severity of the patient's injury. Patients classified as red are considered to need the most immediate attention, followed by patients classified as yellow. Patients classified as green are the least severely injured and patients classified as black are deceased or expectant. After completing initial triage, patients wait at the scene until their designated ambulance arrives. With a resource limited response team, patients often wait for an extended period of time before transport. During this waiting period, patient conditions may deteriorate.
The paper-tag based triage process has many limitations. These include, the wasting of critical time between the time a patient is triaged and the time that information is received by the triage officer, human counting error in counting and tallying triaged patients, the possibility of misuse of paper tags by patients who retriage themselves to a higher priority level, limited visual feedback from the tags at a distance, tags that do not aid in locating a particular patient in a mass of patients, tags that do not distinguish between patients categorized under the same color. Other notable limitations include, categorizing two patients as critical (red) when their respective vital signs designate one to be much worse than the other, no obvious visual differentiation of contaminated versus uncontaminated patients, the inability of responders to track patients who leave the scene without authorization, the non-detection of a lapsed or out of date patient triage status when a patient deteriorates and illegible information on paper tags as a consequence of recording information under time pressure.
The afore-mentioned drawbacks associated with paper tags are overcome by electronic triage tags, sometimes referred to as E-tags. It is noted, however, that while electronic tags overcome the afore-mentioned drawbacks associated with paper tags, they introduce other unique drawbacks. For example, an electronic tag does not show any color coding information when the battery runs out. An electronic tag may be misused by patients who attempt to set their own triage color via the push of a button and the LEDS used with such tags have limited visibility in sunlight. A novel electronic tag of the invention overcomes these and other drawbacks, as will be described below.
While an electronic tag is well suited to mass casualty situations by greatly benefiting a host of patients at a disaster scene by providing patient location and status information, on a mass scale, to medical personnel, its role may be expanded via the integration of vital sign sensors to provide continuous monitoring of a patient's vital signs until they are admitted to a hospital. By integrating vital sign sensors within the electronic tag, medical personnel are provided with a means for simultaneously tracking the vital signs of a large number of patients in an efficient manner. Furthermore, it gives the medical personnel immediate notification of any changes in patient status, such as respiratory failure or cardiac arrest.
One vital sign sensor which has been contemplated for use within an electronic tag is an arrhythmia monitor for detecting patient arrhythmias. As is well known, an arrhythmia monitor provides heart rhythm data, which is supplied to the electronic tag for transmission to a central station for patient monitoring by medical personnel. The applicant has recognized that while the ability to track a patient's heart rhythms and transmit the data in real-time to medical personnel on a mass scale is useful, its usefulness may be enhanced by considering measurements, outside of those conventional measurements to trigger alarms. Specifically, vital sign sensors in present day use typically track a patient's heart rhythms using a set of standard measurements, including, oxygen saturation, pulse pressure and heart rate. While these measurements are very useful in tracking a patient's heart rhythms, the applicant has recognized that certain unconventional measurements, not heretofore considered in the art, may improve the accuracy of automated vital signs monitoring to provide a more accurate picture of a patient's health. Specifically, the applicant has recognized two unconventional measurements that may be useful in providing a more accurate picture of a patient's health. One measurement is a patient's altitude reading (height above sea level). The applicant has recognized that altitude is an important, yet overlooked, parameter in monitoring a patient's heart rhythms, in that it is well known that altitude affects heart rate and blood oxygen concentration and therefore should be considered as a factor in detecting patient arrhythmias. The present invention addresses this limitation by providing a method for dynamically adjusting a patient alarm threshold in a vital sign sensor, such as an arrhythmia monitor, based on a patient's altitude data.
The second unconventional measurement that may prove useful in providing a more accurate picture of a patient's health is a patient's heart rate variability (HRV) reading. It has been shown that patients have a higher survival rate who exhibit HRV values, expressed as HF/LF ratios, of 64+/−12, while terminal patients exhibit HF/LF ratios of 172+/−32. Accordingly, this HRV information may be utilized to adjust an alarm detection parameter of the heart rate monitor sensor to provide a more accurate assessment of a patient's physical condition.